Programmer’s Guide
Publication Number 54645-97000
June 1996 (pdf version Nov 1998)
For Safety information, Warranties, and Regulatory information,
see the pages behind the Index.
© Copyright Hewlett-Packard Company 1996
All Rights Reserved
HP 54645A Oscilloscope and
HP 54645D Mixed-Signal
Oscilloscope
Programming the Oscilloscope
When you attach an interface module to the rear of the HP 54645 A/D
Oscilloscope, it becomes programmable. That is, you can hook a
controller (such as a PC or workstation) to it, and write programs on
that controller to automate oscilloscope setup and data capture. Both
HP-IB (also known as GP-IB, IEEE-488) and RS-232-C interfaces are
available.
The following figure shows the basic structure of every program you
will write for the oscilloscope.
Initialize
To ensure consistent, repeatable performance, you need to start the
program, controller, and oscilloscope in a known state. Without
correct initialization, your program may run correctly in one instance
and not in another. This might be due to changes made in
configuration by previous program runs or from the front panel of the
oscilloscope.
• Program initialization defines and initializes variables, allocates
memory, or tests system configuration.
• Controller initialization ensures that the interface to the
oscilloscope (either HP-IB or RS-232) is properly set up and ready
for data transfer.
• Oscilloscope initialization sets the channel configuration and labels,
threshold voltages, trigger specification and mode, timebase, and
acquisition type.
ii
Capture
Once you initialize the oscilloscope, you can begin capturing data for
analysis. Remember that while the oscilloscope is responding to
commands from the controller, it is not performing acquisitions. Also,
when you change the oscilloscope configuration, any data already
captured is most likely invalid.
To collect data, you use the :DIGitize command. This command clears
the waveform buffers and starts the acquisition process. Acquisition
continues until acquisition memory is full, then stops. The acquired
data is displayed by the oscilloscope, and the captured data can be
measured, stored in trace memory in the oscilloscope, or transferred
to the controller for further analysis. Any additional commands sent
while :DIGitize is working are buffered until :DIGitize is complete.
You could also start the oscilloscope running, then use a wait loop in
your program to ensure that the oscilloscope has completed at least
one acquisition before you make a measurement. HP does not
recommend this because the needed length of the wait loop may vary,
causing your program to fail. :DIGitize, on the other hand, ensures
that data capture is complete. Also, :DIGitize, when complete, stops
the acquisition process so that all measurements are on displayed
data, not on a constantly changing data set.
Analyze
After the oscilloscope has completed an acquisition, you can find out
more about the data, either by using the oscilloscope measurements
or by transferring the data to the controller for manipulation by your
program. Built-in measurements include frequency, duty cycle,
period, and positive and negative pulse width.
Using the :WAVeform commands, you can transfer the data to your
controller. You may want to display the data, compare it to a known
good measurement, or simply check logic patterns at various time
intervals in the acquisition.
iii
In This Book
The HP 54645A/D Programmer’s Guide is your introduction to
programming the HP 54645A Oscilloscope or HP 54645D Mixed-Signal
Oscilloscope using an instrument controller. This book, with the
Programmer’s Reference, provides a comprehensive description of the
oscilloscope’s programmatic interface. The Programmer’s Reference is
supplied as a Microsoft Windows Help file on a 3.5" diskette.
To program the HP 54645A/D, you need an interface module, such as the
HP 54650A, 54651A, or 54652B. You also need an instrument controller that
supports either the IEEE-488 or RS-232-C interface standards, and a
programming language capable of communicating with these interfaces.
This book contains the following information:
Chapter 1, “Introduction to Programming,” gives a general overview of
oscilloscope programming.
Chapter 2, “Programming Getting Started,” shows a simple program, explains
its operation, and discusses considerations for data types.
Chapter 3, “Programming over HP-IB,” discusses the general considerations
for programming the instrument over an HP-IB interface.
Chapter 4, “Programming over RS-232-C,” discusses the general
considerations for programming the instrument over an RS-232-C interface.
Chapter 5, “Programming and Documentation Conventions,” describes the
conventions used in representing the syntax of commands throughout this
book and the HP 54645A/D Programmer’s Reference, and gives an overview
of the oscilloscope command set.
Chapter 6, “Status Reporting,” discusses the oscilloscope status registers and
how to use them in your programs.
Chapter 7, “Installing and Using the Programmer’s Reference,” tells how to
install the HP 54645A/D Programmer’s Reference online help file in
Microsoft Windows, and explains help file navigation.
Chapter 8, “Programmer’s Quick Reference,” lists all the commands and
queries available for programming the oscilloscope.
For information on oscilloscope operation, see the HP 54645A/D User and
Service Guide. For information on interface configuration, see the
documentation for the oscilloscope interface module and the interface card
used in your controller (for example, the HP 82341A interface for IBM
PC-compatible computers).
iv
1
Introduction to Programming
2
Programming Getting Started
3
Programming over HP-IB
4
Programming over RS-232-C
Programming and
5
Documentation Conventions
6
Status Reporting
Installing and Using the
7
Programmer’s Reference
8
Programmer’s Quick Reference
Index
v
vi
Contents
1 Introduction to Programming
Talking to the Instrument 1–3
Program Message Syntax 1–4
Combining Commands from the Same Subsystem 1–7
Duplicate Mnemonics 1–7
Query Command 1–8
Program Header Options 1–9
Program Data Syntax Rules 1–10
Program Message Terminator 1–12
Selecting Multiple Subsystems 1–12
2 Programming Getting Started
Initialization 2–3
Autoscale 2–4
Setting Up the Instrument 2–4
Example Program 2–5
Using the DIGitize Command 2–6
Receiving Information from the Instrument 2–8
String Variables 2–9
Numeric Variables 2–10
Definite-Length Block Response Data 2–11
Multiple Queries 2–12
Instrument Status 2–12
3 Programming over HP-IB
Interface Capabilities 3–3
Command and Data Concepts 3–3
Addressing 3–4
Communicating Over the Bus 3–5
Lockout 3–6
Bus Commands 3–6
Contents–1
Contents
4 Programming over RS-232-C
Interface Operation 4–3
Cables 4–3
Minimum Three-Wire Interface with Software Protocol 4–4
Extended Interface with Hardware Handshake 4–5
Configuring the Interface 4–7
Interface Capabilities 4–8
Communicating Over the RS-232-C Bus 4–9
Lockout Command 4–10
5 Programming and Documentation Conventions
Command Set Organization 5–3
The Command Tree 5–6
Truncation Rules 5–10
Infinity Representation 5–11
Sequential and Overlapped Commands 5–11
Response Generation 5–11
Notation Conventions and Definitions 5–12
Program Examples 5–13
6 Status Reporting
Status Reporting Data Structures 6–5
Status Byte Register (SBR) 6–9
Service Request Enable Register (SRER) 6–11
Trigger Event Register (TRG) 6–11
Standard Event Status Register (SESR) 6–12
Standard Event Status Enable Register (SESER) 6–13
User Event Register (UER) 6–14
Local Event Register (LCL) 6–14
Operation Status Register (OPR) 6–14
Limit Test Event Register (LTER) 6–15
Mask Test Event Register (MTER) 6–16
Histogram Event Register (HER) 6–17
Arm Event Register (ARM) 6–17
Error Queue 6–18
Contents–2
Output Queue 6–19
Message Queue 6–19
Key Queue 6–19
Clearing Registers and Queues 6–19
7 Installing and Using the Programmer’s Reference
To install the help file under Microsoft Windows 7–3
To use the help text and example program files 7–3
To get updated help and program files via the Internet 7–4
To start the help file 7–5
To navigate through the help file 7–5
8 Programmer’s Quick Reference
Contents
Introduction 8–2
Conventions 8–3
Suffix Multipliers 8–3
Commands and Queries 8–4
Index
Contents–3
Contents–4
1
Introduction to Programming
Introduction to Programming
Chapters 1 and 2 introduce the basics for remote programming of an
oscilloscope. The programming instructions in this manual conform to
the IEEE 488.2 Standard Digital Interface for Programmable
Instrumentation. The programming instructions provide the means of
remote control.
To program the HP 54645A/D oscilloscope you must add either an
HP-IB (HP 54650A, for example) or RS-232-C (HP 54651A, for
example) interface to the rear panel.
You can perform the following basic operations with a controller and
an oscilloscope:
• Set up the instrument.
• Make measurements.
• Get data (waveform, measurements, configuration) from the
oscilloscope.
• Send information (pixel image, configurations) to the oscilloscope.
Other tasks are accomplished by combining these basic functions.
Languages for Program Examples
The programming examples for individual commands in this manual are written
in HP BASIC 5.0 or C.
1-2
Introduction to Programming
Talking to the Instrument
Talking to the Instrument
Computers acting as controllers communicate with the instrument by
sending and receiving messages over a remote interface. Instructions for
programming normally appear as ASCII character strings embedded inside
the output statements of a “host” language available on your controller. The
input statements of the host language are used to read in responses from the
oscilloscope.
For example, HP BASIC uses the OUTPUT statement for sending commands
and queries. After a query is sent, the response is usually read in using the
ENTER statement.
Messages are placed on the bus using an output command and passing the
device address, program message, and terminator. Passing the device address
ensures that the program message is sent to the correct interface and
instrument.
The following HP BASIC statement sends a command which sets the
bandwidth limit of analog channel 1 on:
OUTPUT < device address > ;":ANALOG1:BWLIMIT ON"<terminator>
The < device address > represents the address of the device being
programmed. Each of the other parts of the above statement are explained in
the following pages.
1-3
Figure 1-1
Introduction to Programming
Program Message Syntax
Program Message Syntax
To program the instrument remotely, you must understand the command
format and structure expected by the instrument. The IEEE 488.2 syntax
rules govern how individual elements such as headers, separators, program
data, and terminators may be grouped together to form complete
instructions. Syntax definitions are also given to show how query responses
are formatted. Figure 1 shows the main syntactical parts of a typical program
statement.
Program Message Syntax
Output Command
The output command is entirely dependent on the programming language.
Throughout this manual, HP BASIC is used in most examples of individual
commands. If you are using other languages, you will need to find the
equivalents of HP BASIC commands like OUTPUT, ENTER, and CLEAR in
order to convert the examples. The instructions listed in this manual are
always shown between quotation marks in the example programs.
Device Address
The location where the device address must be specified is also dependent
on the programming language you are using. In some languages, this may be
specified outside the output command. In HP BASIC, this is always specified
after the keyword OUTPUT. The examples in this manual assume the
oscilloscope is at device address 707. When writing programs, the address
varies according to how the bus is configured.
1-4
Introduction to Programming
Program Message Syntax
Instructions
Instructions (both commands and queries) normally appear as a string
embedded in a statement of your host language, such as BASIC, Pascal, or C.
The only time a parameter is not meant to be expressed as a string is when
the instruction’s syntax definition specifies <block data>, such as learnstring.
There are only a few instructions which use block data.
Instructions are composed of two main parts:
The header, which specifies the command or query to be sent.
•
The program data, which provide additional information needed to clarify
•
the meaning of the instruction.
Instruction Header
The instruction header is one or more mnemonics separated by colons (:)
that represent the operation to be performed by the instrument. The
command tree in chapter 5 illustrates how all the mnemonics can be joined
together to form a complete header (see chapter 5, “Programming and
Documentation Conventions”).
The example in figure 1 is a command. Queries are indicated by adding a
question mark (?) to the end of the header. Many instructions can be used as
either commands or queries, depending on whether or not you have included
the question mark. The command and query forms of an instruction usually
have different program data. Many queries do not use any program data.
White Space (Separator)
White space is used to separate the instruction header from the program
data. If the instruction does not require any program data parameters, you do
not need to include any white space. In this manual, white space is defined as
one or more spaces. ASCII defines a space to be character 32 (in decimal).
Program Data
Program data are used to clarify the meaning of the command or query. They
provide necessary information, such as whether a function should be on or
off, or which waveform is to be displayed. Each instruction’s syntax definition
shows the program data, as well as the values they accept. The section
“Program Data Syntax Rules” in this chapter has all of the general rules about
acceptable values.
When there is more than one data parameter, they are separated by
commas (,). Spaces can be added around the commas to improve readability.
1-5
Introduction to Programming
Program Message Syntax
Header Types
There are three types of headers:
Simple Command headers
•
Compound Command headers
•
Common Command headers
•
Simple Command Header Simple command headers contain a single
mnemonic. AUTOSCALE and DIGITIZE are examples of simple
command headers typically used in this instrument. The syntax is:
<pr ogram mnemonic><term inator>
Simple command headers must occur at the beginning of a program message;
if not, they must be preceded by a colon.
When program data must be included with the simple command header (for
example, :DIGITIZE ANALOG1), white space is added to separate the data
from the header. The syntax is:
<program mnemonic><separator><program data><terminator>
Compound Command Header Compound command headers are a
combination of two program mnemonics. The first mnemonic selects the
subsystem, and the second mnemonic selects the function within that
subsystem. The mnemonics within the compound message are separated
by colons. For example:
To execute a single function within a subsystem:
:<subsystem>:<function><separator><program data><terminator>
(For example :ANALOG1:BWLIMIT ON)
Common Command Header Common command headers control IEEE
488.2 functions within the instrument (such as clear status). Their
syntax is:
*<co mm an d header>< terminat or >
No space or separator is allowed between the asterisk (*) and the command
header. *CLS is an example of a common command header.
1-6
Introduction to Programming
Combining Commands from the Same Subsystem
Combining Commands from the Same Subsystem
To execute more than one function within the same subsystem a semicolon
(;) is used to separate the functions:
:<su bsystem>:<function><separato r><data>;
<function><separator><data><terminator>
(For example :ANALOG1:COUPLING DC;BWLIMIT ON)
Duplicate Mnemonics
Identical function mnemonics can be used for more than one subsystem. For
example, the function mnemonic RANGE may be used to change the vertical
range or to change the horizontal range:
:ANALOG1:RANGE .4
sets the vertical range of channel 1 to 0.4 volts full scale.
:TIM EB AS E:RANGE 1
sets the horizontal time base to 1 second full scale.
ANALOG1 and TIMEBASE are subsystem selectors and determine which
range is being modified.
1-7
Introduction to Programming
Query Command
Query Command
Command headers immediately followed by a question mark (?) are queries.
After receiving a query, the instrument interrogates the requested function
and places the answer in its output queue. The answer remains in the output
queue until it is read or another command is issued. When read, the answer is
transmitted across the bus to the designated listener (typically a controller).
For example, the query :TIMEBASE:RANGE? places the current time base
setting in the output queue. In HP BASIC, the controller input statement:
ENTER < device address > ;Range
passes the value across the bus to the controller and places it in the variable
Range.
Query commands are used to find out how the instrument is currently
configured. They are also used to get results of measurements made by the
instrument. For example, the command :MEASURE:RISETIME? instructs the
instrument to measure the rise time of your waveform and places the result
in the output queue.
The output queue must be read before the next program message is sent. For
example, when you send the query :MEASURE:RISETIME? you must follow
that query with an input statement. In HP BASIC, this is usually done with an
ENTER statement immediately followed by a variable name. This statement
reads the result of the query and places the result in a specified variable.
Read the Query Result First
Sending another command or query before reading the result of a query causes
the output buffer to be cleared and the current response to be lost. This also
generates a query interrupted error in the error queue.
1-8
Introduction to Programming
Program Header Options
Program Header Options
Program headers can be sent using any combination of uppercase or
lowercase ASCII characters. Instrument responses, however, are always
returned in uppercase.
Program command and query headers may be sent in either long form
(complete spelling), short form (abbreviated spelling), or any combination of
long form and short form.
TIMEBASE:DELAY 1US - long form
TIM:DEL 1US - short form
Programs written in long form are easily read and are almost
self-documenting. The short form syntax conserves the amount of controller
memory needed for program storage and reduces the amount of I/O activity.
Command Syntax Programming Rules
The rules for the short form syntax are shown in chapter 5, “Programming and
Documentation Conventions.”
1-9
Introduction to Programming
Program Data Syntax Rules
Program Data Syntax Rules
Program data is used to convey a variety of types of parameter information
related to the command header. At least one space must separate the
command header or query header from the program data.
<pr ogram mnemonic><sepa rator><data><terminato r>
When a program mnemonic or query has multiple program data a comma
separates sequential program data.
<pr ogram mnemonic><sepa rator><data>,<data><te rminator>
For example, :MEASURE:TVOLT 1.0V,2 has two program data: 1.0V and 2.
There are two main types of program data which are used in commands:
character and numeric program data.
Character Program Data
Character program data is used to convey parameter information as alpha or
alphanumeric strings. For example, the :TIMEBASE:MODE command can be
set to normal, delayed, XY, or ROLL. The character program data in this case
may be NORMAL, DELAYED, XY, or ROLL. The command
:TIMEBASE:MODE DELAYED sets the time base mode to delayed.
The available mnemonics for character program data are always included
with the instruction’s syntax definition. When sending commands, either the
long form or short form (if one exists) may be used. Uppercase and
lowercase letters may be mixed freely. When receiving query responses,
uppercase letters are used exclusively.
Numeric Program Data
Some command headers require program data to be expressed numerically.
For example, :TIMEBASE:RANGE requires the desired full scale range to be
expressed numerically.
For numeric program data, you have the option of using exponential notation
or using suffix multipliers to indicate the numeric value. The following
numbers are all equal:
28 = 0.28E2 = 280e-1 = 28000m = 0.028K = 28e-3K.
When a syntax definition specifies that a number is an integer, that means
that the number should be whole. Any fractional part would be ignored,
truncating the number. Numeric data parameters which accept fractional
values are called real numbers.
1-10
Introduction to Programming
Program Data Syntax Rules
All numbers are expected to be strings of ASCII characters. Thus, when
sending the number 9, you would send a byte representing the ASCII code for
the character “9” (which is 57). A three-digit number like 102 would take up
three bytes (ASCII codes 49, 48, and 50). This is taken care of automatically
when you include the entire instruction in a string.
Embedded Strings
Embedded strings contain groups of alphanumeric characters which are
treated as a unit of data by the oscilloscope. For example, the line of text
written to the advisory line of the instrument with the :SYSTEM:DSP
command:
:SYSTEM:DSP"This is a message."
Embedded strings may be delimited with either single (’) or double (”)
quotes. These strings are case-sensitive, and spaces act as legal characters
just like any other character.
1-11
Introduction to Programming
Program Message Terminator
Program Message Terminator
The program instructions within a data message are executed after the
program message terminator is received. The terminator may be either an NL
(New Line) character, an EOI (End-Or-Identify) asserted in the HP-IB
interface, or a combination of the two. Asserting the EOI sets the EOI control
line low on the last byte of the data message. The NL character is an ASCII
linefeed (decimal 10).
New Line Terminator Functions
The NL (New Line) terminator has the same function as an EOS (End Of String)
and EOT (End Of Text) terminator.
Selecting Multiple Subsystems
You can send multiple program commands and program queries for different
subsystems on the same line by separating each command with a semicolon.
The colon following the semicolon enables you to enter a new subsystem. For
example:
<pr ogram mnemonic><data >;:<program mnemonic><da ta><terminator>
:AN ALOG1:RANGE 0.4;:TIM EBASE:RANGE 1
Combining Compound and Simple Commands
Multiple commands may be any combination of compound and simple
commands.
1-12
2
Programming Getting Started
Programming Getting Started
This chapter explains how to set up the instrument, how to retrieve
setup information and measurement results, how to digitize a
waveform, and how to pass data to the controller.
Languages for Programming Examples
The programming examples in this manual are written in HP BASIC 5.0 or C.
2-2
Programming Getting Started
Initialization
Initialization
To make sure the bus and all appropriate interfaces are in a known state,
begin every program with an initialization statement. HP BASIC provides a
CLEAR command which clears the interface buffer:
CLEAR 707 ! initializes the interface of the instrument
When you are using HP-IB, CLEAR also resets the oscilloscope’s parser. The
parser is the program which reads in the instructions which you send it.
After clearing the interface, initialize the instrument to a preset state:
OUTPUT 707;"*RST" ! initializes the instrument to a preset
state.
Information for Initializing the Instrument
The actual commands and syntax for initializing the instrument are discussed in
the common commands section of the online
Programmer’s Reference
.
HP 54645A/D Oscilloscopes
Refer to your controller manual and programming language reference manual
for information on initializing the interface.
2-3
Programming Getting Started
Autoscale
Autoscale
The AUTOSCALE feature performs a very useful function on unknown
waveforms by setting up the vertical channel, time base, and trigger level of
the instrument.
The syntax for the autoscale function is:
:AUTOSCALE<terminator>
Setting Up the Instrument
A typical oscilloscope setup would set the vertical range and offset voltage,
the horizontal range, delay time, delay reference, trigger mode, trigger level,
and slope. A typical example of the commands sent to the oscilloscope are:
:AN ALOG1:PROBE X10;RANG E 16;OFFSET 1.00<terminato r>
:TIMEBASE:MODE NORMAL;RANGE 1E-3;DELAY 100E-6<terminator>
This example sets the time base at 1 ms full-scale (100µs/div) with delay of
100 µs. Vertical is set to 16V full-scale (2 V/div) with center of screen at 1V
and probe attenuation set to 10.
2-4
Programming Getting Started
Example Program
Example Program
This program demonstrates the basic command structure used to program
the oscilloscope.
10 CLEAR 707 ! Initialize instrument interface
20 OUTPUT 707;"*RST" ! Initialize inst to preset state
30 OUTPUT 707;":TIMEBASE:RANGE 5E-4" ! Time base to 50 us/div
40 OUTPUT 707;":TIMEBASE:DELAY 0" ! Delay to zero
50 OUTPUT 707;":TIMEBASE:REFERENCE CENTER" ! Display reference at center
60 OUTPUT 707;":ANALOG1:PROBE X10" ! Probe attenuation to 10:1
70 OUTPUT 707;":ANALOG1:RANGE 1.6" ! Vertical range to 1.6 V full scale
80 OUTPUT 707;":ANALOG1:OFFSET -.4" ! Offset to -0.4
90 OUTPUT 707;":ANALOG1:COUPLING DC" ! Coupling to DC
100 OUTPUT 707;":TRIGGER:MODE NORMAL" ! Normal triggering
110 OUTPUT 707;":TRIGGER:LEVEL -.4" ! Trigger level to -0.4
120 OUTPUT 707;":TRIGGER:SLOPE POSITIVE" ! Trigger on positive slope
130 OUTPUT 707;":ACQUIRE:TYPE NORMAL" ! Normal acquisition
140 OUTPUT 707;":DISPLAY:GRID OFF" ! Grid off
150 END
Line 10 initializes the instrument interface to a known state.
•
Line 20 initializes the instrument to a preset state.
•
Lines 30 through 50 set the time base mode to normal with the horizontal
•
time at 50 µs/div with 0 s of delay referenced at the center of the graticule.
Lines 60 through 90 set the vertical range to 1.6 volts full scale with center
•
screen at -0.4 volts with 10:1 probe attenuation and DC coupling.
Lines 100 through 120 configure the instrument to trigger at -0.4 volts
•
with normal triggering.
Line 130 configures the instrument for normal acquisition.
•
Line 140 turns the grid off.
•
2-5
Programming Getting Started
Using the DIGitize Command
Using the DIGitize Command
The DIGitize command is a macro that captures data satisfying the
specifications set up by the ACQuire subsystem. When the digitize process is
complete, the acquisition is stopped. The captured data can then be
measured by the instrument or transferred to the controller for further
analysis. The captured data consists of two parts: the waveform data record
and the preamble.
Ensure New Data is Collected
After changing the oscilloscope configuration, the waveform buffers are
cleared. Before doing a measurement, the DIGitize command should be sent to
the oscilloscope to ensure new data has been collected.
When you send the DIGitize command to the oscilloscope, the specified
channel signal is digitized with the current ACQuire parameters. To obtain
waveform data, you must specify the WAVEFORM parameters for the
waveform data prior to sending the :WAVEFORM:DATA? query.
Set :TIMebase:MODE to NORMal when using :DIGitize
:TIMebase:MODE must be set to NORMal to perform a :DIGitize command or to
perform any WAVeform subsystem query. A "Settings conflict" error message
will be returned if these commands are executed when MODE is set to ROLL,
XY, or DELayed. Sending the *RST (reset) command will also set the time base
mode to normal.
The number of data points comprising a waveform varies according to the
number requested in the ACQuire subsystem. The ACQuire subsystem
determines the number of data points, type of acquisition, and number of
averages used by the DIGitize command. This allows you to specify exactly
what the digitized information contains.
2-6
Programming Getting Started
Using the DIGitize Command
The following program example shows a typical setup:
OUTPUT 707;":ACQUIRE:TYPE AVERAGE"<terminator>
OUT PUT 707;":ACQUIRE:CO MPLETE 100"<terminator>
OUT PUT 707;":WAVEFORM:S OURCE ANALOG1"<terminato r>
OUT PUT 707;":WAVEFORM:F ORMAT BYTE"<terminator>
OUT PUT 707;":ACQUIRE:CO UNT 8"<terminator>
OUT PUT 707;":WAVEFORM:P OINTS 500"<terminator>
OUTPUT 707;":DIGITIZE ANALOG1"<terminator>
OUT PUT 707;":WAVEFORM:D ATA?"<terminator>
This setup places the instrument into the averaged mode with eight averages.
This means that when the DIGitize command is received, the command will
execute until the signal has been averaged at least eight times.
After receiving the :WAVEFORM:DATA? query, the instrument will start
passing the waveform information when addressed to talk.
Digitized waveforms are passed from the instrument to the controller by
sending a numerical representation of each digitized point. The format of the
numerical representation is controlled with the :WAVEFORM:FORMAT
command and may be selected as BYTE, WORD, or ASCII.
The easiest method of transferring a digitized waveform depends on data
structures, formatting available and I/O capabilities. You must scale the
integers to determine the voltage value of each point. These integers are
passed starting with the leftmost point on the instrument’s display. For more
information, see the waveform subsystem commands and corresponding
program code examples in the online HP 54645A/D Oscilloscopes
Programmer’s Reference.
Aborting a Digitize Operation Over HP-IB
When using HP-IB, a digitize operation may be aborted by sending a Device
Clear over the bus (CLEAR 707).
2-7
Programming Getting Started
Receiving Information from the Instrument
Receiving Information from the Instrument
After receiving a query (command header followed by a question mark), the
instrument interrogates the requested function and places the answer in its
output queue. The answer remains in the output queue until it is read or
another command is issued. When read, the answer is transmitted across the
interface to the designated listener (typically a controller). The input
statement for receiving a response message from an instrument’s output
queue typically has two parameters; the device address, and a format
specification for handling the response message. For example, to read the
result of the query command :ANALOG1:COUPLING? you would execute the
HP BASIC statement:
ENTER <device address> ;Setting$
where <device address> represents the address of your device. This would
enter the current setting for the channel one coupling in the string variable
Setting$.
All results for queries sent in a program message must be read before another
program message is sent. For example, when you send the query
:MEASURE:RISETIME?, you must follow that query with an input statement.
In HP BASIC, this is usually done with an ENTER statement.
Sending another command before reading the result of the query causes the
output buffer to be cleared and the current response to be lost. This also
causes an error to be placed in the error queue.
Executing an input statement before sending a query causes the controller to
wait indefinitely.
The format specification for handling response messages is dependent on
both the controller and the programming language.
2-8
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